1. Field of the Invention
The invention refers to a method and to a device for identifying traffic-relevant information in a moving vehicle. Traffic-relevant information can in particular be traffic signs which, for example, indicate the maximum permissible speed. In addition to traffic signs as such, the invention in principle refers to all information which can be perceived visually and which instructs drivers to behave in a certain way. It is envisaged that the image data of a visual sensor, particularly an optical camera oriented in the direction of driving, and the map data of a navigation system are each pre-evaluated for said identification and the results of said pre-evaluation are combined and interpreted.
2. Description of the Related Art
Many developments in modern motor vehicles serve to make the driver aware of traffic-relevant information during driving to make driving safer on the whole. This includes in particular the indication of the currently valid maximum speed, which can be used merely as additional information for the driver, but also to generate danger warnings or to directly influence the vehicle's speed either by braking or accelerating.
Navigation systems have been known for quite a time, which in addition to the course and type of roads also include a valid speed limit. The quality of this speed limit included in the road maps as a fixed value largely depends, however, on how complete and up to date the digitalized maps are. Experience shows that it takes quite a time until new speed information is included in the digital map data if speed limits are changed. An even bigger problem is that digital road maps are often stored in navigation systems and users tend to update them relatively seldom as this involves considerable costs.
From a system point of view, it is even more difficult to detect temporary information, for example that provided by overhead sign bridges on motorways showing information and speed limits which are adapted to the prevailing traffic conditions or at road work sites. This varying information is particularly safety-relevant as the speed limits or other rules conveyed to the driver of a motor vehicle in this way are adapted to the prevailing traffic conditions or a current dangerous situation. This information cannot be detected, however, by the navigation systems described above.
In this respect, DE 199 38 261 A1 proposes to take into account temporary local conditions or individual impressions of the driver for a specific route by enabling temporary local conditions which can be entered automatically or manually, such as, for example, temporary speed limits, traffic jam warnings, or the like, to be placed as variable electronic route markers which are displayed and/or influence automatic operation of the motor vehicle when the route is driven again. There is the special problem, however, that this information is normally not available until the route is driven a second time and cannot be retrieved when the driver uses a route he/she does not know for the first time.
DE 199 38 267 A1 proposes a system for electronically identifying traffic signs, which are detected using a video camera, interpreted, and displayed within the vehicle. It is intended that the traffic signs which have been identified in this way are stored in a navigable electronic route map at their respective locations to improve the quality of the digital map and to enable traffic signs and navigated route data to be better correlated. In addition, DE 199 38 266 A1 proposes that a logical analysis is carried out if a traffic sign or one out of several traffic signs is not identified without doubt, in such a manner that other parameters of the prevailing traffic conditions and/or other traffic signs are also taken into account for the interpretation and the lowest possible speed limit is determined. This data is stored according to the respective location, the driver being allowed to make corrections.
DE 103 54 910 A1 discloses an autonomous vehicle which is provided with a self-steering navigation system and takes into account traffic signs placed at the side of the road. For this purpose, a camera records the traffic signs placed at the side of the motorway. An image processor analyses these images and determines the sign contents contained in the traffic signs. At the same time, map information concerning the motorway is stored in a navigation data base. An electronic steering unit with artificial intelligence now determines a current position of the self-moving motor vehicle and a road condition using the map information stored in the navigation data base and the sign contents read by the image processor. On the basis of the result determined in this way, a processor then controls a steering operation, a speed reduction/increase operation, and an operation related to the self-steering navigation function. This system is so far restricted to motorways, however, as the signs used there are limited and can be interpreted and identified much easier than on many other roads or streets, particularly within towns and cities where signing is often confusing.
EP 1 114 371 B1 describes a method and a device for identifying traffic signs and for navigation. If traffic signs are identified, traffic sign identification data is created and navigation data for locating the vehicle is provided and the traffic sign identification data and the navigation data is compared with each other and updated, if required. For this purpose, the data is supplied to a shared evaluation unit which determines a currently valid speed limit and generates control signals, if appropriate.
All systems described above have the drawback, however, that the data acquired during image data recognition is very extensive and the data processing described often cannot be done in real time, at least if all image data is evaluated.
For this reason, EP 1 145 186 B1 proposes a system having at least one map-based navigation system and a system for displaying the contents of traffic signs which have been recorded by a camera, wherein the system for traffic sign identification begins to work with increased power if map-based information indicates that the vehicle passes an area which is problematic in respect of traffic sign identification. For this purpose, a multiprocessor system for utilizing free data capacity throughout the motor vehicle is used. There is the problem, however, that the increased computing capacity is only available if the underlying map-based system already contains information that a situation might arise which could be difficult to evaluate in terms of image recognition.